Extraction of hydrocarbon oils



Sept. 11, 1956 Filed April 27, 1955 PERCENT MES/TYLE/VE EXTRACTED J. l. SLAUGHTER ETAL 2,762,751

EXTRACTION OF HYDROCARBON OILS 2 Sheets-Sheet 1 Q 60 60 Q L, E u 5 k 40 a 40 s g) PART/AL PRESSURE 5E psl'g.

Fig. 1

Ja/m Slaughter David A. McCall/0y INVENTORS.

ATTORNEY p 11,1956 J. SLAUGHTER ET AL 2,762,751

EXTRACTION OF HYDROCARBON OILS 2 Sheets-Sheet 2 Filed April 27, 1955 United States Patent ExrnAcrroN or HYDRO'CARBON OILS John I. Slaughter, Whiting, Ind, and David A. Mc'Caulay,

Chicago, 331., assignors to Standard Oil Company, Chicage, lll., a corporation of Indiana Application April 27, 1955', Serial No. 504,206

9 Claims. (Cl. 196-13) This invention relates to the extraction of hydrocarbon oils and in particular it concerns the treatment of hydrocarbon oils with fluorophos'phoric acid and BFs as the selective solvent.

Hydrocarbon oils such as petroleum and the various fractions thereof, coal tar distillates, shale oils and the like are generally comprised of a mixture of different types of compounds. They may contain aromatic, aliphatic, and alicyclic hydrocarbons as well as sulfur compounds, nitrogen compounds and the like. It is frequently desirable that hydrocarbon fractions be produced free from one or more of several types of these compounds. The petroleum refiner generally desires to remove sulfur compounds from petroleum or the various fractions thereof, such as gasoline, kerosene, burning oils, etc. The presence of aromatic hydrocarbons in kerosene causes the latter to burn with a smoky flame and removal of the aromatic hydrocarbons is often necessary. Condensed ring aromatics lower the viscosity index of lubricating oil stocks and consequently their removal from such a stock is highly desired. The quality of various other petroleum fractions available to the refiner should similarly be refined to remove undesired components such as the aromatic hydrocarbons, sulfur compounds and the like.

Hydrocarbon oils frequently contain components such as polyalkyl benzenes and polynuclear aromatic whose recovery may be desirable. The separation of polyalkyl benzenes and polynuclear aromatics in high purity has become more important in recent years because of the growing demand for particular aromatic hydrocarbons for use in the manufacture of synthetic materials. The manufacture of fibres, plastics, and synthetic intermediates frequently dctates that a specific aromatic hydrocarbon (free of the isomers usually associated therewith) be employed as the initial raw material. The recovery of a single isomer of an aromatic hydrocarbon from its admixture with various other hydrocarbons including its isomers is an exceedingly difiicult problem.

An object of this invention is to provide a method of treating hydrocarbon oils to remove undesirable components therefrom. Another object is to provide a method for extracting aromatic hydrocarbons and sulfur compounds from hydrocarbon oils. A further object is to provide a process for the separation of polyalkyl ben- Zenes according to their structural configuration. Numerous other objects and advantages of the present invention will be apparent from the detailed description thereof.

It has been discovered that polyalkyl benzenes, polynuclear aromatics and organic sulfur compounds can be extracted from hydrocarbon oils by the use of a solvent consisting of monofluorophosphoric or difluorophosphoric acid and BF3 employed in excess of a certain minimum amount. The BFs is employed in excess of that amount which saturates the phosphoric acid. This excess amount of BF3 is at least one mole per mole of extractable component which is desired to be removed from the hydrocarbon oil undergoing treatment. The BF3 is preferably 2,762,751 Patented Sept. 11, 1956 employed in an amount suflicient to provide a partial pressure of BFs in the extraction zone of above about p. s. i. g. usually about 100 to 3000 p. s. i. g. The fluorophosphoric acid, preferably difluorophosphoric acid, is employed in an amount at least sufiicient to form separate extract and rafiinate phases. The extraction may be carried out at a temperature between. about 40 F. and 500 F., preferably at a temperature below about F. After thorough mixing of the phosphoric acid and BFs with the hydrocarbon oil, the raflinate and heavier extract phases which are formed are separated. The raflinate and heavier extract phases are separated while in the presence of BFa in an amount in excess of that required tosaturate the fluorophosphoric acid. Components such as polyalkyl benzenes, polynuclear aromatics or sulfur compounds which have been extracted from the oil and are now contained in the extract phase are separated therefrom.

It has also been found that the extracted components can be separated from the extract phase by removing BF3 therefrom. This may be done by reducing the B1 3 pressure on the separated extract phase as BF3 is flashed off, extracted components are sprung from our solvent. The components which are thus sprung can be settled and then removed from the heavier acid layer. The acid layer and the BF3 may be recycled to the extraction process.

We have also discovered that it is possible to separate polyalkyl benzenes from each other as Well as from aliphatic and alicyclic hydrocarbons which may be contained in the oil. The separation of polyalkyl benzenes is based on their structural configuration. It depends to a great extent upon the number of alkyl substituents in the polyalkyl benzene molecule and their location. in the benzene ring.

The fluorophosphoric acids which may be employed in our invention are monofluorophosphoric acid or difluorophosphoric acid. They should contain no water. Di fluorophosphoric acid is preferred over monofiuorophosphoric acid because the former acid enables our solvent to have a higher capacity for extracted. components as well asa greater selectivity for certain of the components. In addition the difluorophosphoric acid is less: viscous and is more volatile. The difluorophosphoric acid is thus easily handled. It can be purified, when necessary, by distillation, preferably at a temperaturebelow about F. The monofiuorophosphoric acid also tends to produce side reactions of the components being extracted.

The fluorophosphoric acid should be employed in an amount in excess of its solubility in the oil. The amount of fluorophosphoric acid which may be employed will depend generally upon the amount of extractable components which one desires to remove from the hydrocarbon oil undergoing treatment, and the particular fiuorophosphorie acid used. If difluorophosphoric acid is used, then one mole of extractable component is removed for each tWomoles of the difluorophosphoric acid employed. When using monofluorophosphoric acid, one mole of extractable component is removed per every mole of monofluorophosphoric acid employed. In general the larger the amount of fiuorophosphoric' acid which is employed the larger will be the amount of extractable components extracted from the oil undergoing treatment. Approximately 5 to 1000 volume percent of fluorophos phoric acid based upon feed oil may be employed. Usually about 50 to 400 volume percent of the fluorophosphori'c acid based on oil is used. At the higher ratios of fluorophosphoric acid to oil, our solvent has an enhanced selectivit'y for the extractable components.

When BF}; is passed into the fiuorophosphoric acid,

BF:; is readily absorbed. The acid becomes saturated with BFs if exposed to a BF partial pressure of 5 p. s. i. g. While not wishing to be bound by any theory, it is believed that a complex or compound is formed between the fluorophosphoric acid and BFa which is quite stable so long as it is subject to a BF3 partial pressure of 5 p. s. i. g. or higher. It appears that one mole of BFz complexes with two mols of difiuorophosphoric acid whereas one mole of BF complexes with only one mole of monofluorophosphoric acid.

In practicing our invention, we employ the BFa-saturated fluorophosphoric acid (which is believed to have the above defined compositions) together with additional amounts of BFa. This additional amount of ER; employed (which is in excess of that required to saturate the fluorophosphoric acid) is at least one mole of BF: per mole of extractable component which is desired to be removed from the oil. It is to be understood herein that our solvent consists of the BFa-saturated fluorophosphoric acid (saturated usually at 5 p. s. i. g. BFx) together with additional amounts of BFz in excess of that required to saturate the fluorophosphoric acid. Without any intention of limiting the scope of the present invention, it is our belief that a coordination compound or adduct hereinafter called a complex is formed which consists of the BFa-saturated fluorophosphoric acid, the BFa in excess of that required to saturate the fluorophosphoric acid and the extractable component. The complexes formed have been visualized as follows:

The complexes which are formed with the various extractable components have varying degrees of stability. To increase the amount of complex formed, BFa is employed in an amount larger than would theoretically be necessary to complex with each mole of extractable component. The larger the amount of BFs which is used in our extraction process, the greater is the amount of extractable components which are extracted from the oil. In practicing our invention the hydrocarbon oil is contacted with the BFs-saturated fluorophosphoric acid in the presence of excess BFs. This excess BFa which is employed in the contacting Zone is usually an amount sufficient to provide a partial pressure of BFs in the contacting zone of at least about 100 p. s. i. g. BFs partial pressures of 100 to 3000 p. s. i. g. or higher may be employed. To attain a high degree of extraction of extractable components, a BFs partial pressure between about 500 and 2000 p. s. i. g. may be used.

The contacting of the hydrocarbon oil with the fluorophosphoric acid and BF3 may be effected at any temperature provided the oil and fluorophosphon'c acid are in the liquid phase. The BFs-saturated fluorophosphoric acid is liquid at temperatures lower than -40 F. Although it is possible to extract at temperatures below about 40 F. (and even lower temperatures are included within the scope of our invention), it is not usually practical to do so since the oil and phosphoric acid become too viscous. The contacting may be carried out at temperatures as high as 500 F. although temperatures below about 125 F. are preferred in order to avoid side reactions due to the catalytic effects of our solvent. In general the capacity of the solvent for extractable components decreases as the contacting temperature is increased. We prefer to operate at temperatures of from about 50 to about 100 F.

The hydrocarbon oil is contacted with our solvent for i a time sufficient for the solvent to extract extractable components from the oil. This time will vary, dependent upon the efl'lciency of contacting or mixing. Generally the contacting or mixing time may be from 5 to minutes in each extraction stage. Contact times greater than 1 hour may be employed but usually produce no greater efficiency in extraction. A very long contact time especially at a high temperature may result in side reactions of the hydrocarbons due to the catalytic activity of our solvent.

Because of the high viscosity of some hydrocarbon oils, it may be desirable to carry out the contacting thereof with our solvent in the presence of an inert diluent. Reducing the viscosity of the oil improves the contacting efliciency in the contacting Zone and enables a greater degree of extraction. In addition the raffinate phase of a lower viscosity hydrocarbon oil can be separated more cleanly and rapidly from the extract phase. The diluent should be substantially inert to the fluorophosphoric acid and BFa. It should not be affected by the catalytic action of our solvent. Additionally, the diluent should be readily separable by distillation from the hydrocarbon oil although in some instances, it may be desirable to leave the diluent in the refined oil. Suitable diluents are pentane, hexane, petroleum ether, cyclohexanes, benzenes, toluene, and various naphtha fractions low in extractable components. Materials such as heptane or octane may suitably be used when the contacting is carried out at about ambient temperatures.

After the hydrocarbon oil has been mixed with our solvent for a time suflicient for the acid to remove extractable components from the oil, the mixture is settled. The solvent containing extractable components settles from the lighter oil. The heavier extract phase is then separated from the lighter raffinate phase. It is highly important that the phases be separated while in the presence of or under the influence of BE; in excess of that necessary to saturate the fluorophosphoric acid. The phases are preferably separated while under a partial pressure of BFa of above about p. s. i. g., usually about 100 to 3000 p. s. i. g. Separation of the phases is usually carried out under the same partial pressure of BFa and at about the same temperatures as existed during the extraction step. If desired, the extract phase may be washed with non-extractable hydrocarbons which serve the function of stripping out components from the extract phase which are not so strongly absorbed therein. The hydrocarbon diluents discussed in the preceding paragraph may be used for this purpose. This washing or stripping of the extract phase improves the selectivity of our solvent extraction process.

After separation of the extract phase from the raifiuate phase, the extract phase is treated to recover extractable components therefrom. The extracted components can be sprung from the extract phase by reducing the partial pressure of BF: on the extract phase. As BFa is vented from the separated extract phase, extracted components separate therefrom. The less stable complexes formed between the extractable components and our selective solvent are the first to decompose. As the partial pressure of BFs in the separated extract phase is lowered, additional amounts of extracted components are sprung from the selective solvent and form a separate and lighter layer. It is readily apparent that the reduction of the partial pressure of BFa may be stopped at any point to control the amount of extractable components which are sprung from the extract phase. A number of fractions of oil having different characteristics may be separated from the extract phase by reducing the partial pressure of BFa, separating the extracted components which have been sprung, and repeating the cycle. During the springing step an inert hydrocarbon may be employed to wash the extract phase to insure the substantially complete removal of sprung hydrocarbons from the selective solvent. The pressure on the separated extract phase can thus be reduced to atmospheric pressure to flash off BFa and spring extracted components. If desired the pressure on the s separated extract phase may be reduced to as low as 50'to 200 mm. abs. in the springing step to insure complete springing of extracted components from the extract phase. Thus vacuum distillation may be used to separate extracted components from the extract phase. Although it is not a preferred method, the extracted components may be sprung from the separated extract phase by treating it with water, preferably cold water or ice. The water dilution method is less desirable since it renders the fiuorophosphoric acid unfit for further use.

The BF3 may be rapidly removed from the separated extract phase at the temperature employed in the extraction step and generally at a somewhat higher temperature. Thus, while BFa may be removed from the extract phase at temperatures as high a 500 F. (cracking and other reactions of the extracted components may occur at this high temperature), it is preferred to effect flashing of the BF3 from the extract phase at a tempertaure below about 200 F. The BF3 which is thus flashed from the separated extract phase may be recycled for further use in the extraction step. Likewise the fluorophosphoric acid layer may be recycled. It is of course necessary to separate extracted components from the fully saturated selective solvent before reusing for further extraction, otherwise no additional extraction will occur.

If the pressure on the separated extract phase is reduced to atmospheric pressure to flash oif BR; and spring extracted components, the fluorophosphoric acid layer which is decanted and reused repeatedly tends to become contaminated with a tarry material. If difluorophosphoric acid is employed, it may be purified by distilling the difluorophosphoric acid layer and leaving behind the tarry material. The distillation of the difluorophosphoric acid is preferably practiced at a temperature below about 175 F. viz. distillation under a slight vacuum. It is not possible to remove the tarry impurities from a monofluorophosphoric acid layer because of decomposition of the monofiuorophosphoric acid when its distillation is attempted.

The feed to our process may be a hydrocarbon oil which contains extractable components. Polyalkylbenzenes, polynuclear aromatics and organic'sulfur compounds and the like can be removed selectively from the oil by the process of our invention. Any of a wide variety of hydrocarbon oils can be charged to the extraction zone. Various fractions obtained from the distillation of petroleum, for example, naphthas, kerosenes, heater oil, lube oils, etc. or the crude oil itself, may be used as the feed stock. Hydrocarbon oil derived from the treatment of the above materials, for example, naphthas obtained from catalytic cracking or hydroforming or rafiinates or extracts from the solvent refining of naphthas or kerosenes, may be employed as the feed oil. The boiling point of the hydrocarbon oil charged is of no especial consequence so long as it contains extractable components. Suitably it may be between about 200 and 750 F. Shale oil and its various fractions are a suitable feed to the process. The so-called light oil from the coking of a coal may also be employed. The liquid products produced during the hydrogenation of coal may be employed as a charging stock to our process.

The raflinate from our process will usually be the desired product because of its reduced sulfur content and its reduced aromatic content. This is usually the case when the charging stock is a lube oil stock, a kerosene or a high sulfur stock which it is desired to desulfurize. Cycle gas oils are also extracted by our process to produce a rafiinate of reduced sulfur and aromatic content which is an excellent stock for recycling to catalytic cracking.

It may be desirable to extract hydrocarbon oils for the purpose of recovering aromatic hydrocarbons from the oil. Thus, the extracted components rather than the raffinate oil may be the desired fraction. It is possible by our invention to extract polyalkyl benzenes from other of BF; existent in the separated close boiling'hydrocarbons. Thus an extract oil rich in polyalkyl benzenes may be recovered and employed as high anti-knock engine fuel. Our solvent does not seem to complex with benzene or toluene alone. If there are extractable components in the feed, e. g. polyalkylbenzenes, then benzene and/or toluene are dissolved in the extract phase in larger amounts. The presence of complexed components improves their solubility.

We have also discovered that polyalkylbenzenes can be separated from each other as well as from aliphatic and alicyclic hydrocarbons. The separation of polyalkylbenzenes depends upon their structural configuration. In general the complexes which are formed between the polyalkylbenzenes and our solvent become more stable with an increase in the number of alkyl substituents in the benzene ring. Those benzenes which are substituted in the 1,3-position and in the 1,3,5-position form complexes with the solvent which are more stable than those formed from polyalkylbenzenes having the same number of alkyl substituents but substituted in different positions in the benzene ring. The stability of the complex of a polyalkyl benzene with fluorophosphoric acid and BFz is reflected by the pressure at which it dissociates. The higher its dissociation pressure, the less stable is the complex. If the extraction of the polyalkylbenzenes and the separation of the extract phase are both carried out at a pressure above the dissociation pressure of a complex of a specific polyalkylbenzene with fluorophosphoric acid and BFa, but at lesser partial pressure of BF3 than the dissociation pressure of a complex of a different polyalkylbenzene with the fiuorophosphoric acid and BFs, a separation between the two polyalkylbenzenes can be made. By taking advantage of the diifering stabilities of the complexes of various polyalkyl benzenes with the fiuorophosphoric acid and BFs, a number of separations between polyalkylbenzenes can be effected. 1,3-dialkyl benzenes can be separated from dialkyl benzenes having their alkyl substituents in other positions in the benzene ring. Similarly 1,3,5-trialkyl'benzenes can be separated from trialkyl benzenes having alkyl substituents in other positions in the benzene ring. In addition 1,3,5-trialkyl benzenes can be separated from any of the dialkyl benzenes. Also l,2,3,5-tetra-alkyl benzene can be separated from any dialkyl or trialkyl benzenes and from isomeric tetra-alkyl benzenes. Penta-alkyl benzene can be separated from any polyalkyl benzene having a lesser number of alkyl substituents in the benzene ring, and hexaalkyl benzene is separable in an analogous manner from polyalkyl benzenes having a lesser number of alkyl substituents.

In another modification of our extraction process, substantially all of the polyalkyl benzenes (or whatever portion of the polyalkylbenzenes is desired) can be extracted from the hydrocarbon oil. After separating the extract phase the BFs pressure thereon may be partially released to spring or form an additional raffinate phase. The rafiinate phase will contain polyalkylbenzenes whose complexes with our solvent are less stable at lower BFs partial pressures. For example, highly aromatic naphtha fractions such as the product of hydroforming may be extracted with our solvent under BFs partial pressures of 2000 p. s. i. g.

or higher to produce an extract phase containing substantially all of the polyalkyl benzenes contained in the hydroformate. The partial pressure extract phase is then reduced to about 500 p. s. i. g. whereupon a lighter rafiinate layer is formed. The raifmate layer is rich in dialkyl and other more completely substituted polyalkyl benzenes which are not substituted in the 1,3,5-positions. The extract is rich in polyalkyl benzenes substituted in the 1,3,5-positions including triand higher polyalkyl benzenes. Thus substantially complete separation of polyalkyl benzenes may be made from a hydrocarbon oil and the polyalkyl benzenes may subsequently be separated highly branched alkyl into fractions which are enriched in differing polyalkyl benzenes.

Our solvent also has catalytic activity for causing the shifting of alkyl groups on alkyl benzenes. The more substituents are more mobile. This mobility, which is reflected by the extent of conversion of the alkylbenzenes, increases with temperature, thoroughness of mixing, contact time, ratio of fluorophosphoric acid to alkylbenzene, and increasing chain length of the alkyl substituents in the alkyl benzene. When the alkyl substituent contains more than about 4 carbon atoms, there is a tendency for the side chain to isomerize and even crack. Isopropyl, sec-butyl, and tert-butyl side chains become highly mobile at about 70 F. Temperatures in the neighborhood of 85 or 100 F. are necessary before ethyl side chains become highly mobile. An even higher temperature viz. around 125 F. is needed in order to render methyl side chains highly mobile.

It has been found that our solvent-catalyst is capable of rapidly disproportionating alkyl benzene. When our solvent-catalyst is employed (preferably under a BFs partial pressure of 100 p. s. i. g. or higher) at a temperature of to200 F., alkyl benzene may be disproportionated to produce the symmetrical 1,3,5 -trialkylbenzene in a large proportion. A temperature below 200 F. is preferred in the contacting step to minimize the formation of other isomeric trialkyl benzenes. The fluorophosphoric acid is employed in an amount of from 0.25 to 10, preferably about 3 volumes per volume of alkyl benzene feed. A contact time of from 0.25 to hours, suitably about 2 to 6 hours may be employed. For example, ethylbenzene may be contacted with about 3 volumes of (lifluorophosphoric acid under a BF3 partial pressure of 1500 p. s. i. g. for about 2 hours at about 80 F. to produce 1,3,5-triethylbenzene in large amounts. The production of diethylbenzene is minor.

It has also been discovered that polyalkyl benzenes such as trialkyl benzene and tetra-alkyl benzene can be isomerized to produce polyalkyl benzene having a high concentration of those polyalkyl benzenes which have alkyl substituents in the 1,3,5-positions in the benzene ring. Our solvent-catalyst is used at a BFa partial pressure of about 100 p. s. i. g. or higher. Reaction temperatures of 0 to 200 F. may be employed. A temperature higher than 200 F. causes the formation of larger amounts of polyalkyl benzenes having alkyl substituents other than in the 1,3,5-positions. In general the tetra-alkyl benzenes require somewhat higher temperatures to effect isomerization than do the trialkyl benzenes. The fluorophosphoric acid is employed in an amount of from 0.25 to 10, preferably about 3 volumes per volume of alkyl benzene feed. Contact times of 0.25 to 10 hours or more, preferably about 2 to 6 hours may be used. For example, trimethyl benzenes may be isomerized to 1,3,5-trirnethyl-benzene by contacting the feed with about 3 volumes of difluorophosphoric acid under a BFs partial pressure of about 500 p. s. i. g. at a temperature of about 125 F. for about 4 hours.

We have also discovered that if ethylbenzene and metaxylene plus orthoxylene or paraxylene are contacted with our solvent-catalyst, it is possible to produce a xylene fraction which is enriched in the xylene isomers other than metaxylene, and an ethylxylene fraction rich in the 1,3,5-isomer. The reaction is carried out preferably at a temperature of about 70 to 125 F. although a temperature as low as 0 F. and as high as about 200 F. may be employed. Our solvent-catalyst is employed while using a BB; partial pressure of 100 p. s. i. g. or higher, suitably 2000 p. s. i. g. While the volumetric ratio of fluorophosphoric acid to alkyl benzene feed may vary from 0.25 to 10:1, a preferred ratio is about 3:1. A reaction time of 1 to 10 or more hours, preferably about 4 to 8 hours is employed. The extract phase recovered is rich in ethylxylene and the raflinate phase is rich in 8 l xylenes other than meta-xylene. In a process modification, the reaction is carried out in two stages. A BFa partial pressure of 2000 p. s. i. g. and a short contact time e. g., 1 to 2 hours, is used in the first step, following which a phase separation is made. The raftinate phase is enriched in xylene isomers other than meta-xylene. The extract phase is reacted for an additional length of time e. g. 1 to 10 hours, to produce a high yield of 1,3,5- ethylxylene. After the reaction has been completed, the products may then be recovered by removing BFs from the reaction product and separating the hydrocarbon layer, from the fluorophosphoric acid layer. Alternatively, the products may be recovered after the reaction has been completed by separating an extract phase rich in 1,3,5-ethylxylene from the rafiinate phase which contains large amounts of benzene and ethylbenzene.

We have also found that mononuclear aromatics can be alkylated with olefins containing 2 to 4 carbon atoms to produce polyalkyl benzenes having alkyl substituents in the 1,3,5-positions in the benzene ring. The alkylation may be carried out at a temperature of 0 to 200 F., the higher molecular weight olefin being employed at the lower temperatures. A temperature of about 70 F. is used when propylenes or butylenes are employed and a temperature of about F. is employed when ethylene is used. The BFa is employed in our solvent-catalyst in amounts to provide a partial pressure of BFs higher than about 100 p. s. i. g. The fluorophosphoric acid to hydrocarbon volumetric ratio may be from 0.25 to 10:1 e. g. 3:1. To prepare the 1,3,5-trialkylbenzene, at least the stoichiometric amount of necessary olefins should be introduced. The olefin should be introduced slowly e. g. over a period of 0.5 to 10 hours or more. For example, metaxylene may be alkylated with ethylene to produce 1,3,5-ethylxylene. Benzene may be converted in a very large proportion to 1,3,5-triethylbenzene by contacting benzene with about three moles of ethylene and about three volumes of difluorophosphoric acid under a BB; partial pressure of 500 p. s. i. g. and a temperature of about 75 F. for four hours.

A number of experiments were performed which demonstr-ate the effectiveness of our invention. The procedure which was followed in the experiments was as follows: The feed oil was charged to an autoclave (Hastel loy construction preferred) of 250 cc. capacity. Fluorophosphoric acid was then added to the autoclave in the desired amount. The autoclave was sealed and BFa was passed into the autoclave until the desired partial pressure of ER; was attained within the autoclave. The contents were then mixed for the desired length of time which was usually between /2 to 4 hours, depending on the effectiveness of mixing. The contents of the autoclave were then settled for about an hour and the heavier extract layer was then withdrawn while maintaining the partial pressure of BFa within the autoclave. The raffinate layer was then recovered. The pressure on the separated extract phase was then reduced to atmospheric pressure and BFa was flashed from the extract phase and passed into a liquid nitrogen trap for recovery. From the extract phase now at about atmospheric pressure were recovered the extracted components. In certain experiments the extracted components, which had been sprung on depressuring the extract phase, were recovered by decantation of the layer thereof which formed above the fluorophosphoric acid layer. In other experiments the extract phase was passed into ice at Dry Ice temperatures to spring extracted components from the extract phase.

The first series of experiments demonstrate the eficctiveness of our invention in reducing the sulfur content and the aromatic content of hydrocarbon oils. The hydrocarbon oil employed in run No. 1 was a heavy catalytic cycle gas oil. A West Texas virgin gas oil was employed in run No. 2. The feed to run No. 3 consisted of 4.04 volume percent diphenyl sulfide in n-heptane. The

gas oils which were employed had the following inspections:

In extracting the above feed stocks, approximately 100 cc. of feed and cc. of difluorophosphoric acid were used. A temperature of about 75 to 80 F. and a BFa partial pressure of 500 p. s. i. g. were maintained within the autoclave. The contents were mixed for about 2 hours and then settled for one hour to effect stratification. The heavier extract phase was separated and BFa was released therefrom. In runs N0. 1 and 2 the extracts were then passed over ice at Dry Ice temperatures. The extracted oils were then analyzed and the extent of desulfurization and dearomatization of the feed oils was then determined. The treating loss as measured by the volume of oil lost to the extract phase was measured. The results obtained are shown in Table I which follows:

The excellent desulfurization ability of our solvent is readily apparent. In each run more than 90% of the sulfur compounds were removed from the oil. The treating loss in run No. 3 was only 4% which corresponds approximately with the 4.04 volume percent of organic sulfur compound in the feed. The high selectivity of our solvent for organic sulfur compounds makes it very useful in petroleum refining. The ability to remove aromatic hydrocarbons from the charging stock as evidenced by the results of run No. 2 makes our process useful in producing a raffinate oil which is an improved charging stock to catalytic cracking for the production of gasoline.

The value of our process in improving the quality of lubricating oil stocks has also been demonstrated. It has been shown that our process is capable of improving the viscosity index by a very considerable amount. In run No. 4 a 20W base stock having a gravity of 22.5 API, a viscosity at 100 F. of 311.4 SSU, a viscosity index of 50, a sulfur content of 1.61 weight percent, and an NPA color of 3, was extracted with our selective solvent under conditions identical with those discussed in the preceding desulfurization and dearomatization experiments. About 66% of the oil was recovered as a ratfinate oil (34 volume percent treating loss). This oil had a viscosity at 100 F. of 101.7 SSU, a viscosity index of 98, a sulfur content of 0.18 weight percent (which corresponds to a desulfurization of 92.6%) and was water-white in color. Thus our invention is applicable to the extraction of lube oil stocks to improve viscosity index, lower the sulfur content, and improve the color.

In order to compare the effectiveness of monofluorophosphoric acid and difluorophosphoric acid in our selective solvent, experiments were performed wherein equal volume mitxures of mesitylene and n-heptane were extracted. In both runs cc. of the hydrocarbonmixture and 25 cc. of the fluorophosphoric acid were employed. The temperature of extraction was about 75 F. In run No. 5 wherein monofluorophosphoric acid was employed, a BFs partial pressure of 550 p. s. i. g. was used. In run No.6 a partial pressure of BZ-z of 520 p. s. i. g. was used. The mixing time was about 1.5 to 2 hours. The contents of the autoclave were settled for about an hour and the extract and rafiinate phases separately recovered. The extract phase was passed into ice at Dry Ice temperatures to spring extracted components. The results obtained in these runs are shown in Table II which follows:

Table II Percent Percent Percent Run Mesit- Mesit- Mesit- Selec- No. Acid ylene ylene ylene tivity in feed In extract in rafiialpha 1 nate 5 Monofluorophosphoric 50 21 4. 3 6 Difluorophosphoric 50 99+ 8 12. 5

1 Alpha (a)=mole fraction mesitylene in cxtract+mole fraction mesitylene in raflinate.

Difiuorophosphoric acid is preferred over monofluorophosphoric acid in our solvent since it has a higher capacity for extractable components and a greater selectivity for them.

The importance of employing BFa in excess of the amount necessary to saturate the fluorophosphoric acid has been demonstrated in .a number of experiments. These experiments also demonstrate the effectiveness of our selective solvent for separating one polyalkyl benzene from a diiferent polyalkyl benzene. The feed to each run was an equal volume mixture of mesitylene, m-xylene, and n-heptane. In each run an equal volume of feed and difluorophosphoric acid were used. The extraction was conducted at a temperature of about 75 F; and under a partial pressure of BF3 which differed in each run and was in the range of 5 p. s. i. g. to 483 p. s. i. g. The reaction mixture was agitated for about 1 to 2 hours and then settled for an equivalent length of time. The extract phase was separated while subject to the same partial pressure of BFs as was employed during the extraction operation. The hydrocarbon was liberated from the extract phase by depressuring. Analyses of the sprung extract oil and the raflinate oil were then made. The results obtained are shown in Table III which follows:

Table III Percent Distribu- Run No. BFII, Mesitylene tion 00- p. s. i. g Extracted efiicient 1 1 Distribution coefficient is MEXOOM XRl where M stands for (Gene. Mn) (Cone. XE)

mesitylene, X stands for rn-xylene, and subscripts E and R stand for extract and raifinate respectively.

The importance of conducting the extraction under a high partial pressure of BFa, i. e. so that BE; in excess of that required to saturate the acid is present, is readily apparent from the above data. These data are graphically illustrated in Figure 1. The ability of our solvent to extract trialkyl benzenes having alkyl substituents in the 1,3,5-p0sitions in the benzene ring from position isomers of the trialkyl benzenes has also been demonstrated. Approximately 100 cc. of a mixture of isomeric trimethyl benzenes (Eastman Kodak Blue Label) was mixed with 50cc. of difluorophosphoric acid under a partial pressure of BFs of p. s. i. g. A temperature of about 75 F. was maintained in the autoclave. A mixing time of about 2 hours and a settling time of about 1 hour were used. The extract phase was withdrawn while under the 150 p. s. i. g. partial pressure of BFs.

The'pressure on the extract phase was reduced to atmospheric thus springing the extracted components from a. heavier difluorophosphoric acid layer. Approximately 6.5 cc. of oil were thus sprung. The raffinate oil amounted to 93 cc. The components present and their distribution by mole per cent in the feed, extract, and raflinate set forth in Table IV which follows:

The results show the phenomenal selectivity of our solvent for polyalkylbenzenes which have their alkyl substituents substituted in the 1,3,5-positions in the benzene ring. Similar results have been demonstrated in selectively extracting 1,3,5-triethylbenzene from its position isomers.

A fraction of the naphtha produced by hydroforming a petroleum naphtha was employed as feed in an additional experiment. The hydroformate fraction boiled over the range of about 270 to 305 F. Approximately 1,000 cc. of feed was agitated with 100 cc. of difluorophosphoric .acid for about l hour while under a BFs partial pressure of 550 p. s. i. g. The autoclave contents were settled for about thirty minutes and the extract and raffinite phases separated while under the partial pressure of BFs. The separated extract phase was then depressured to atmospheric pressure and 17 cc. of extracted oil were thus sprung and recovered. The components present in the feed and in the extract are shown below in 'Table V:

Non-aromatic hydrocarbons From the analyses of the feed and extract it can be seen that our solvent is capable of extracting meta-xylene from the other xylenes and mesitylene from the other trimethylbenzenes. Because the contacting time was excessive our solvent-catalyst caused some reactions of the alkylbenzenes, as evidenced by the presence of a large amount of l,3-dimethyl-5-ethylbenzene in the extract. The extract may be fractionated to recover separately, a xylene fraction rich in meta-xylene, a mesitylene stream, and an ethylxylene fraction rich in 1,3-din1ethyl-5-ethylbenzene.

. A preferred embodiment of our invention will be described with relation to Figure 2 which is a schematic representation of an adaption of our process for extracting mesitylene from a fraction of hydroformed naphtha. Valves, pumps, and the like have been omitted from the flow diagram of Figure 2 for purposes of clarity.

Difluorophosphoric acid is introduced from source 11 by way of valved line 12 into vessel 13 which is capable of withstanding high pressures. Anhydrous BFs is passed from source 14 by way of valved line 16 into vessel 13. Because saturation of the fluorophosphoric acid with BFa is an exothermic reaction, vessel 13 is provided with 12 cooling means 17 to maintain the temperature at not higher than about F. The BFs is introduced into vessel 13 so that a partial pressure of BFa of about 500 p. s. i. g. is maintained therein. The solvent (which consists of BFa-saturated phosphoric acid and BFs in partial pressure of 500 p. s. i. g.) is passed by way of valved line 18 into the extractor 19 at a point near its top.

Because our solvent is corrosive to ordinary metals, it is usually necessary to employ some material of construction which is not aflected by the solvent. Aluminum and Hastelloy have been found to be outstanding with regard to resistance to corrosion by our selective solvent. Monel is also highly satisfactory.

Extractor 19 is a single-stage countercurrent extraction column. The hydrocarbon feed is passed from source 21 by way of valved line 22 into extractor 19 at a point not far above its bottom. The hydrocarbon feed employed is a fraction of hydroformed naphtha which boils between about 270 and 400 F. It contains a substantial amount of trimethylbenzenes including mesitylene, other alkylated aromatic hydrocarbons, and associated aliphatic and alicyclic hydrocarbons. The selective solvent is thoroughly mixed with the hydrocarbon feed at a temperature of about 75 F. for about 15 minutes. Approximately 0.5 liquid volume of our selective solvent is introduced per volume of hydrocarbon feed. The BFs partial pressure is maintained at about 500 p. s. i. g. within extractor 19 by introducing B1 3 at vertically spaced points in the reactor through a manifolding system represented by valved lines 23, 23a, and 23b. The extract phase which is at the bottom of extractor 19 is countercurrently Washed with heptane. Heptane is introduced from source 24 by way of valved line 26 into extractor 19 at a point below the hydrocarbon feed inlet 22 and above the withdrawal line 27 by which the extract phase is removed. About 0.2 volume of heptane is employed per volume of hydrocarbon feed.

The extract phase is removed from extractor 19 while under a BF3 partial pressure of 500 p. s. i. g. and passed by way of line 27 to heater 28. The extract phase is heated to about F. and then passed by way of line 29 into extract decomposer 31. In decomposer 31 the pressure on the extract phase is reduced to atmospheric pressure which causes BFs to flash from the extract phase. The flashed BF3 is removed from decomposer 31 and recycled by Way of line 32 either to extractor 19 or into valved line 16 for forming fresh solvent in vessel 13. The liquid extract phase remaining in decomposer 31 is passed by way of line 33 into settler 34. The heavier acid layer is removed from settler 34 and passed by way of valved line 36 into valve line 12 whereby it is recycled to vessel 13 for the formation of further amounts of selective solvent. Whenever the acid layer becomes contaminated with an undesirable amount of tar or sludgy material, a portion or all of the acid layer may be withdrawn from valved line 36 and passed by way of valved line 3'7 to fractionator 33. A stream of difluorophosphoric acid is removed overhead from fractionator 3S and passed by way of line 39 into line 36 for recycle to form further amounts of solvent. A tarry material is removed from the bottom of fractionator 38 and discarded. The lighter hydrocarbon layer is removed from settler 34 and passed by way of line 41 into coalescer 42. Coalescer 42 may be a rock salt coalescer or other means effective for removing residual amounts of acid from the oil. The recovered acid is removed from coalescer 42 byway of line 43. if desired it may be reused for the extraction of additional amounts of hydrocarbon feed. The extracted oil is removed from coalescer 42 and passed by way of line 44 into fractionator 46. Here the residual amount of BFs and other lowboiling components including any xylenes present are distilled overhead. A bottoms fraction containing high boiling materials such as tetrarnethylbenzeues, ethyltrimethylbenzenes, and the like, is removed. A side-cut consisting of about 95% purity mesitylenc is recovered and passed by way of line 47 to storage, not shown. The rafiinate phase is removed from extractor 19 and passed by way of line 48 to means for recovering heptane and rafiinate oil. The heptane may be recycled to the extractor. The raffinate oil may be neutralized and washed prior to sending to storage.

Thus having described our invention what is claimed is:

1. A process of treating a hydrocarbon oil to separate an extractable component selected from the class consisting of polyalkyl benzenes, polynuclear aromatics, and organic sulfur compounds which process comprises contacting in a contacting zone at a temperature below about 125 F. said hydrocarbon oil containing at least one of said extractable components with about to 1000 volume per cent based on said oil of a fluorophosphoric acid selected from the group consisting of monofluorophosphoric acid and difluorophosphoric acid and ER in an amount suflicient to provide a partial pressure thereof in the contacting zone of between about 100 and 3000 p. s. i. g., forming a raflinate phase and a heavier extract phase, separating said phases while under said partial pressure of BFs into a rafiinate phase and a heavier extract phase containing extractable components and reducing the partial pressure of BF; on said extract phase to spring extracted components from the extract phase.

2. The process of claim 1 wherein said contacting is carried out in the presence of a hydrocarbon diluent that is substantially inert to the action of the phosphoric acid and BFs.

3. The process of claim 1 wherein said extractable component is an organic sulfur compound.

4. The process of claim 1 wherein said hydrocarbon oil is a lubricating oil stock.

5. The process of claim 1 wherein said extractable component is a polyalkyl benzene.

6. The process of claim 1 wherein said hydrocarbon oil contains a mixture of polyalkyl benzenes and wherein only a portion of said polyalkyl benzenes are extracted in said extract phase, the remainder of said polyalkyl benzenes being contained in said raffinate phase.

7. The process of claim 1 wherein said hydrocarbon oil is a petroleum fraction boiling within the range of about 270 and 400 F. which contains trialkyl benzenes,

wherein a polyalkyl. benzene substituted in the 1,3,5- positions with alkyl groups is recovered from said extract phase.

8. A process of treating a hydrocarbon oil to separate an extractable component selected from the class consisting of polyalkyl benzenes, polynuclear aromatics, and organic sulfur compounds which process comprises contacting said hydrocarbon oil containing at least one of said extractable components with a fluorophosphoric acid selected from the group consisting of mono-fluorophosphoric acid and difluorophosphoric acid and 131%, said fiuorophosphoric acid being employed in an amount in excess of its solubility in said hydrocarbon oil, carrying out said contacting at a temperature below about 500 F. and under a partial pressure of BE; in excess of about p. s. i. g., forming a rafrinate phase and a heavier extract phase containing extractable components, and separating said phases.

9. A process of treating a hydrocarbon oil to separate an extractable component selected from the class consisting of polyalkyl benzenes, polynuclear aromatics and organic sulfur compounds which process comprises contacting at a temperature below about 500 F. said hydrocarbon oil containing at least one of said extractable components with a fiuorophosphoric acid selected from the group consisting of monofiuorophosphoric acid and difluorophosphoric acid and BFs, said fiuorophosphoric acid being employed in an amount of about 5 to 1000 volume percent based on said oil, carrying out said contacting under a partial pressure of BFs of between about 100 and 3000 p. s. i. g., forming a raffinate phase and a heavier extract phase containing extractable components, separating said phases while subject to said BFs partial pressure, and removing extracted components from said extract phase.

References Cited in the file of this patent UNITED STATES PATENTS 2,495,851 Lien et al Jan. 31, 1950 2,671,047 Arnold et al Mar. 2, 1954 FOREIGN PATENTS 1,065,848 France Jan. 13, 1954 

1. A PROCESS OF TREATING A HYDROCARBON OIL TO SEPARATE AN EXTRACTABLE COMPONENT SELECTED FROM THE CLASS CONSISTING OF POLYALKYL BENZENES, POLYNUCLEAR AROMATICS, AND ORGANIC SULFUR COMPOUNDS WHICH PROCESS COMPRISES CONTACTING IN A CONTACTING ZONE AT A TEMPERATURE BELOW ABOUT 125* F. SAID HYDROCARBON OIL CONTAINING AT LEAST ONE OF SAID EXTRACTABLE COMPONENTS WITH ABOUT 5 TO 1000 VOLUME PER CENT BASED ON SAID OIL OF A FLUOROPHOSPHORIC ACID SELECTED FROM THE GROUP CONSISTING OF MONOFLUOROPHOSPHORIC ACID AND DIFLUOROPHOSPHORIC ACID AND BF3 IN AN AMOUNT SUFFICIENT TO PROVIDE A PARTIAL PRESSURE THEREOF IN THE CONTACTING ZONE OF BETWEEN ABOUT 100 AND 3000 P.S.I.G., FORMING A RAFFINATE PHASE AND A HEAVIER EXTRACT PHASE, SEPARATING SAID PHASES WHILE UNDER SAID PARTIAL PRESSURE OF BF3 INTO A RAFFINATE PHASE AND A HEAVIER EXTRACT PHAE CONTAINING EXTRACTABLE COMPONENTS AND REDUCING THE PARTIAL PRESSURE OF BF3 ON SAID EXTRACT PHASE TO SPRING EXTRACTED COMPONENTS FROM THE EXTRACT PHASE. 